The objective of this study is to examine the cancer mortality experience in the United States relative to cancer etiology. Special emphasis is placed upon the selection of areas in the U.S. for intensive study. Publications from this area of interest have facilitated the design of ongoing analytical investigations to test specific etiologic hypotheses. Rates for multiple myeoloma were found to be highest in urban areas and lowest in rural areas; positive associations were seen with indices of socioeconomic level and percentage of residents with Scandinavian ancestry. Leukemia mortality rates were high among whites in the North and South Central States, among nonwhites in the Northeast and Midwest. These geographic patterns persisted after adjusting for urbanization and socioeconomic gradients and for ethnic correlations. Occupational determinants may be involved. A significant positive correlation was seen between PMRs for canine bladder cancer and the overall level of industrial activity in counties with veterinary medical teaching hospitals. Canine bladder cancer could be a sentinel condition whose investigation in certain locales might lead to early identification of carcinogenic hazards in the general environment.